Apparatuses for encoding an image may compress the image to perform encoding as a method of efficiently decoding the image. A quantization process may be included in such a compression process. When quantization is performed, although deterioration in image quality may occur relative to an original image, image compression may be efficiently performed by performing compression based on whether a user may largely recognize deterioration in image quality. That is, a technology for performing high-efficiency compression without subjective deterioration in image quality has been proposed by performing relatively more compression on portions that are difficult to visually recognize by analyzing an image itself.